Optical sensing device and method for manufacturing an optical sensing device

Abstract

An optical sensing device comprises a substrate carrying a first and a second photodetector stack comprises a band-pass filter, a decoupling layer arranged on the band-pass filter and a lower dielectric mirror arranged on the decoupling layer. The filter stack comprises a spacer stack with a primary spacer layer arranged on the lower dielectric mirror, comprising a first dielectric material and covering the photodetector array. The spacer stack comprises a first spacer layer comprising the first dielectric material, wherein a first segment of the first spacer layer is arranged on the primary spacer layer and covers the second photodetector but not the first photodetector. The filter stack comprises an upper dielectric mirror arranged on the spacer stack.

1 . An optical sensing device comprising a semiconductor substrate carrying a photodetector array with at least a first and a second photodetector and a filter stack arranged on the substrate and covering the photodetector array, the filter stack comprising
 a band-pass filter, a decoupling layer arranged on the band-pass filter and a lower dielectric mirror arranged on the decoupling layer, wherein each of the band-pass filter, the decoupling layer and the lower dielectric mirror covers the photodetector array;   a spacer stack comprising
 a primary spacer layer arranged on the lower dielectric mirror, comprising a first dielectric material and covering the photodetector array; and 
 a first spacer layer comprising the first dielectric material, a first segment of the first spacer layer being arranged on the primary spacer layer and covering the second photodetector but not the first photodetector; and 
   an upper dielectric mirror arranged on the spacer stack.   
     
     
         2 . The optical sensing device according to  claim 1 , wherein each part of the first spacer layer is in direct contact with the upper dielectric mirror. 
     
     
         3 . The optical sensing device according to  claim 1 , wherein the decoupling layer is adapted to decouple the band-pass filter from filter elements which are formed by sections of the spacer stack, the lower dielectric mirror and the upper dielectric mirror. 
     
     
         4 . The optical sensing device according to  claim 1 , wherein the photodetector array further comprises a third and a fourth photodetector and the spacer stack further comprises
 a second spacer layer comprising the first dielectric material, a first segment of the second spacer layer being arranged on the primary spacer layer and covering the third and the fourth photodetector but none of the first and the second photodetector;   a second segment of the first spacer layer being arranged on the second spacer layer and covering the fourth photodetector but none of the first, the second and the third photodetector.   
     
     
         5 . The optical sensing device according to  claim 1 , wherein each of the lower and the upper dielectric mirror consists of mirror layers, containing the first dielectric material and further mirror layers containing a second dielectric material with a second refractive index being different from a first refractive index of the first dielectric material, wherein the mirror layers and the further mirror layers are arranged alternatingly. 
     
     
         6 . The optical sensing device according to  claim 5 , wherein at least some of the mirror layers and at least some of the further mirror layers have a thickness corresponding to an optical distance being equal to one quarter of a specified center wavelength. 
     
     
         7 . The optical sensing device according to  claim 6 , wherein
 a first filter element is formed by a section of the lower dielectric mirror covering the first photodetector, a section of the primary spacer layer covering the first photodetector and a section of the upper dielectric mirror covering the first photodetector; and   second filter element is formed by a section of the lower dielectric mirror covering the second photodetector, a section of the primary spacer layer covering the second photodetector, the first segment of the first spacer layer and a section of the upper dielectric mirror covering the first photodetector.   
     
     
         8 . The optical sensing device according to  claim 7 , wherein a value of a first pass wavelength of the first filter element is determined by a thickness of the primary spacer layer and a value of a second pass wavelength of the second filter element is determined by total thickness of the primary spacer layer and the first spacer layer. 
     
     
         9 . The optical sensing device according to  claim 8 , wherein the first pass wavelength and the second pass wavelength lie within a stop-band of the lower dielectric mirror and within a stop-band of the upper dielectric mirror. 
     
     
         10 . The optical sensing device according to  claim 8 , wherein the first pass wavelength and the second pass wavelength lie within a pass-band of the band-pass filter. 
     
     
         11 . The optical sensing device according to  claim 5 , wherein the band-pass filter consists of band-pass layers containing the first dielectric material and further band-pass layers containing the second dielectric material, wherein the band-pass layers and the further band-pass layers are arranged alternatingly. 
     
     
         12 . The optical sensing device according to  claim 1 , wherein the first and the second photodetector are configured to
 detect light incident on the optical sensing device and passing through the upper dielectric mirror, the spacer stack and the lower dielectric mirror; and   to generate a first channel signal and a second channel signal, respectively, based on the detected light.   
     
     
         13 . The optical sensing device according to  claim 12 , further comprising a readout circuit configured to generate, depending on the first and the second channel signals, at least one spectral signal indicative of a spectral composition of the incident light. 
     
     
         14 . The optical sensing device according to  claim 1 , wherein
 the photodetector array comprises at least M photodetectors with M=2̂N and N being a positive integer number;   the primary spacer layer covers the at least M photodetectors;   the spacer stack comprises N spacer layers comprising the first dielectric material, wherein
 the N spacer layers are patterned and form together with the primary spacer layer M spacer elements; 
 a first spacer element of the M spacer elements consists of a section of the primary spacer layer covering the first photodetector; 
 each the M spacer elements except for the first spacer element comprises segments of a different subset of the N spacer layers and covers one of the at least M photodetectors. 
   
     
     
         15 . A method for manufacturing an optical sensing device, wherein the method comprises
 providing a semiconductor wafer with a semiconductor substrate, the substrate carrying a photodetector array with at least a first and a second photodetector;   depositing a band-pass filter, depositing a decoupling layer on the band-pass filter and depositing a lower dielectric mirror on the decoupling layer, wherein each of the band-pass filter, the decoupling layer and the lower dielectric mirror covers the photodetector array;   depositing a spacer stack, the deposition of the spacer stack comprising
 depositing on the lower dielectric mirror a primary spacer layer comprising a first dielectric material and covering the photodetector array; and 
 depositing and structuring by means of a first lift-off sequence a first spacer layer comprising the first dielectric material, a first segment of the first spacer layer being arranged on the primary spacer layer and covering the second photodetector, but not the first photodetector; and 
   depositing an upper dielectric mirror on the spacer stack.   
     
     
         16 . The method according to  claim 15 , wherein each part of the first spacer layer is in direct contact with the upper dielectric mirror. 
     
     
         17 . The method according to  claim 15 , wherein the decoupling layer is adapted to decouple the band-pass filter from filter elements which are formed by sections of the spacer stack, the lower dielectric mirror and the upper dielectric mirror. 
     
     
         18 . The method according to  claim 15 , wherein
 the photodetector array further comprises a third and a fourth photodetector;   the deposition of the spacer stack further comprises, before depositing the first spacer layer, depositing and structuring by means of a second lift-off sequence a second spacer layer comprising the first dielectric material, a first segment of the second spacer layer being arranged on the primary spacer layer and covering the third and the fourth photodetector but none of the first and the second photodetector; and   a second segment of the first spacer layer is arranged on the second spacer layer and covers the fourth photodetector but none of the first, the second and the third photodetector.   
     
     
         19 . The method according to  claim 15 , wherein
 the photodetector array comprises at least M photodetectors with M=2̂N and N being a positive integer number;   the primary spacer layer covers the at least M photodetectors;   the deposition of the spacer stack comprises depositing and structuring by means of N lift-off sequences N spacer layers comprising the first dielectric material, wherein each of the N spacer layers covers a different subset of the M photodetectors, each subset comprising M/2 of the at least M photodetectors.